This invention relates to sprinkler heads and, more particularly, to sprinkler heads that nutate while they rotate to minimize the “donut effect” prevalent with conventional non-nutating sprinkler heads.
Various nutating or wobbling sprinkler head designs have been available but with potential shortcomings that can nullify the very nutating effect that makes such sprinklers attractive in the first instance. Examples of known nutating or wobbling sprinkler heads may be found in prior U.S. Pat. Nos. 5,381,960; 5,950,927; and 6,932,279. Commonly owned U.S. Pat. Nos. 5,439,174; 5,588,595; 5,671,885; 6,267,299; and 6,439,477 provide further examples of nutating or wobbling sprinkler heads.
One problem often encountered with sprinklers of this type relates to stalling at start up or during normal operation. Stalling occurs when the water distribution plate of the sprinkler head fails to tilt at start up, or ceases tilting during operation, thereby simply rotating and distributing a stream particularly susceptible to the “donut effect” where the wetted pattern area is shaped like a solid ring around a dry center. When nutating or wobbling sprinklers operate as designed, the nutating action tends to fill in the pattern in a substantially uniform manner. Thus, it is critical that the water distribution plate reliably and consistently remain in a tilted orientation while rotating to achieve the desired nutating action.